White Fondant

I love making fondant flowers for all my cakes, but am having trouble keeping it snow white. I make the MM fondant and it is really nice and white at first, but it turns an off white after it has been stored for a short time. There is a noticable difference between the fresh and the older batch. Can anyone help me with this problem?

The food coloring might be the best bet. My fondant and gumpaste do the same thing, there's a difference in color after a while and it's enough to notice if you have the new and old right next to each other. I think it's either the gelatin or tylose in it, it will just discolor eventually no matter what you do. The white food color might stop that.